The present invention relates to a surface treating apparatus, a surface treating method and a semiconductor device manufacturing method. More particularly, the present invention relates to an apparatus for and a method of treating a solid surface using a thermally excited molecular beam.
In the surface treating method which uses a thermally excited molecular beam, a gas containing a halogen, such as SF.sub.6, is heated by means of a furnace to excite rotational, translational and vibrating energies of molecules thereof (hereinafter, excitation of rotational, translational and vibrating energies of molecules being referred to as thermal excitation of molecules), and such a gas is injected into a vacuum to form a beam. That beam is used to treat a solid surface. Since the thermally excited molecules are highly reactive, the use of such a molecular beam in the etching of a solid surface, which is the manufacturing process of semiconductor devices, greatly increases the etching rate as compared with a case in which non-thermally excited molecular beams. Since the thermal energy level of the molecules is low as compared with the energy level of electrons or ions in a plasma, the solid is less damaged in this surface treating technique as compared with the conventional surface treating methods which use charged particles. Also, the adverse effect of the electric charges to the solid can be eliminated because the thermally excited molecular beam is the neutral particle beam. The surface treating techniques which use the thermally excited molecular beam have been disclosed in, for example, U.S. Pat. No. 4,901,667.
This conventional technique will now be described.
FIGS. 1 and 2 are similar to FIGS. 5 and 6 of U.S. Pat. No. 4,901,667. Referring first to FIG. 1, this surface treating apparatus includes a vacuum chamber 101, a sample base 103 for holding a sample 102, a leak valve 104 for introducing a gas 112, a gas heating means including a heat source 105 and a heating furnace 106, and a thin hole 107 for injecting the gas into a vacuum. In this apparatus, the heating means 105 is provided externally to the reaction chamber 101 in order to prevent radiation of heat and flying of the contaminant to the sample 102. The outer wall of the gas heating furnace 106 protrudes from the vacuum chamber, and this necessitates provision of a vacuum sealing 109 between the gas heating furnace 106 and the vacuum chamber 101. A flange 108 prevents the vacuum sealing 109 from making direct contact with the gas heating furnace 106. A cooling means 110 prevents thermal damage to the vacuum sealing. A connecting portion 111 facilitates replacement of the gas heating furnace 106.
However, in this method, the heating means is exposed to air and is easily oxidized, as stated in the specification of the above-described U.S. patent. In a case where the heating means uses a heater made of, for example, tungsten, tungsten is oxidized and thereby breaks easily when heated to high temperatures in the air.
FIG. 2 shows a structure which is an improvement on the apparatus shown in FIG. 1. In this structure, the heating means 105 is placed in a chamber 102 that can be evacuated in order to prevent flying of the contaminant and radiation of heat to the sample 102 as well as oxidation of the heating means. A partitioning plate 123 having holes 122 through which beams can pass is provided between the chamber 121 where the heating means is provided and the reaction chamber 101 so that both chambers can be exhausted separately although they cannot be hermetically separated from each other in a complete form.